PYCNOGONIDA. 



27 



of its own, seven glands on each side of the animal, fig. 17 a. a. Of Pall, hastata I have two figures, pi. I, 

 fig. 18 — 19, which show a more advanced stage, the third pair of ambulatory legs being here already 

 very much lengthened, so that all three pairs seem to have been developed at the same time; from 

 the first figure, however, it is distinctly seen, that there must have been an interval between the 

 second and third pair. In the species of Pscudopalloic the delay of the third pair of ambulatory legs, 

 is, however, much more considerable, as is already shown by the two figures of Pscudop. spimpcs, 

 pi. I, fig. 8-~9. As to the further development I shall refer to the figures of Pscudop. circularise pi. I, 

 fig. 10 — 14. In the two first of these figures the development has not gone farther than to the re- 

 presentation of Pscudop. spiuipcs, given in the preceding figure, but in fig. 12 it has gone much farther. 

 Here the two foremost pairs of ambulatory legs have been fully developed (of the four uniform legs 

 only the foremost right leg has been drawn), while the leg of the third pair is still only a bag-shaped 

 process with a characteristic stiff bristle implanted on the upper side, a little before the point. In the 

 same figure is furthermore seen the processes of the intestinal canal into the three pairs of legs, 

 going in the wholly drawn foremost leg quite into the outermost joint. No traces of embryonal legs 

 are seen, but neither, what is to be emphasized, is the least beginning of the imaginal fore limbs to 

 be found. In the fore edge of the first abdominal ganglion, or the suboesophageal ganglion are seen 

 through the epidermis a pair of short processes, as also a pair of still smaller, ballshaped appendages 

 farther back, inside the side margin; but no nervous fibres are seen to arise from these processes and 

 appendages. The anus is now distinctly open. Fig. 13 represents the same larva from the upper side, 

 but witli the two foremost pairs of ambulatory legs completely removed; the oculiferous tubercle with 

 the eyes is distinctly seen. Fig. 14 gives the last phase of the same stage. Here also the third pair 

 of ambulatory legs have been almost fully developed, only the last joint but one wanting; but still 

 the lower side of the first segment of the trunk is as naked as in the preceding phase, fig. 12. 



Kroyer, in his second essay, Bidr. til Kundsk. 0111 Pycnog. (1844), has given a description of 

 what he calls the first and second stages of Pallene infer media (= Pscudopallcuc circularis); but the 

 description itself, and still more the figures in Gaimard's work of travel (1849) pl-39t fig 2 a. a. — cl, of 

 which figures Kroyer, no doubt, has been thinking, show distinctly that we here have two phases 

 of the same larval stage, i.e. of the second stage, of which Kroyer treats, and the figures given bv 

 Kroyer of the animals, fig. 2, a. and c. are completely answering to my figures 8 and 12 — 13, only 

 that in the first of my figures I have also the byssus-thread, and in the last one also the eyes. The 

 omission of the eyes may, I think, be due to the bad preservation of the larva whereby the elements 

 of sight have been removed from their position on the oculiferous tubercle; at least I believe to have 

 found these elements strewn round in the trunk of the original piece of Krover which I have had 

 occasion for examining, as well as the fresh specimen drawn here. Otherwise I think it to be the 

 real or apparent want of genuine embryonal legs, and the contemporaneous development of the two 

 foremost pairs of ambulatory legs, by which these latter get a certain resemblance to the former limbs, 

 which has induced Kroyer not only to suppose this degree of the second larval stage to be the 

 first, but also, what is much worse, led him to the wrong supposition of the real embryonal legs 

 developing into the two foremost pairs of ambulatory legs. But this same mistake, on the other 

 hand, has freed Kroyer from the present common wrong interpretation of the imaginal fore limbs 



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